Improvement in ventilating-caps



. L. F. BETTS.

Ventilating Cap.

NO. 168,961. Patented 0ct.19,1875.

WITNESSES UNITED STATES PATENT QFFIGE.

LEWIS F. BETTS, OF CHICAGO, ILLINOIS.

IMPROVEMENT IN VENTlLATlNG-CAPS.

Specification forming part of Letters Patent No. 168,961, dated October19, 1875; application filed September 28, 1875.

To all whom it may concern:

Be it known that I, LEWIS F. BETTS, of Chicago, in the county of Cookand State of Illinois, have invented a Ventilating-Gap, of which thefollowing is a specification:

This invention relates to that class of chimney-caps which are designedto exhaust or cause an outward flow of air from said chimney whereversaid cap is exposed to moving currents of the surrounding atmosphere,from whatever direction they may come; and it consists of a series offlat parallel annular rings disposed one above another, decreasing insize and covered by a disk.

It is well known as a law of fluid motion that a moving current passingacross the open mouth of a tube will tend to exhaust the same. Thiseffect is observed in chimneys which have a stronger draft during highwinds than at other times. Practically, the problem is to preventwind-currents which are moving in other than horizontal lines fromblowing into and down chimneys or ventilating-pipes. Heretofore, no capor cowl has been produced which, without machinery or moving parts, andof cheap construction, could control the air-currents without regard totheir direction, and cause the desired exhaustion. The fundamentalrequirements appear to be a thin edge for the chimney, across which themoving current must pass, and defleeting-plates capable of reducing allcurrents to a horizontal direction. I therefore surround the upper endof the ventilating-pipe A with an annular plate or flange, B, thesurface of which is perpendicular to the axis of the pipe A. The pipe Aprojects above the surface of the flange B about one-fourth (5;) of aninch, as shown at 1). Above the flange 13, and parallel thereto, is asimilar annular flange, G, having a less diameter than B, and a smallcylindrical flange or ledge, c, projecting upward around the centralopening of said flange, and above the flange (l is still another flange,D, similar in all respects, except that it is of less diameter, and thewhole series is surmounted by a disk, E, which covers the centralopenings in the several annular flanges. The relative sizes of thevarious annular flanges are determined by the diameter of the pipe A,and, without designing to be limited strictly to the relative dimensionshereinafter given, I think them to be very nearly it not the very best,and constructed by an easy formula which renders it a simple process tolay out the proper dimensions for any sized flue. The width of theflange B is equal to onehalf the length of the diagonal of thesemidiameter of the pipe A, as shown in the diagram, Fig. 3. The severalannular flanges are equal in width, and the inner edges cut the diagonalabove named. The space intervening between the flanges is equal toone-third the width of flange B.

It is apparent that from whatever direction the wind may come upon a capconstructed as described, it will be deflected to pass over the centralopenings in a direction perpendicular to the axis, or very nearly so,and the small ledges c afford the sharp or thin edges required to enablethe moving current to produce the necessary exhaustion.

The flanges B (J D E are supported and retained in proper position bythree or more strips, F, bent as shown at proper intervals, to receivethe edges of the flanges, to which it may be secured by a rivet, whilethe lower end of said strip F is riveted fast-to the side of the pipe A,and thus forms a brace for the whole structure.

Having described my invention, what I claim as new isl. The com binationof a series of flat parallel annular flanges, B O D E, provided withledges c c and disposed perpendicularly to the axis of the pipe A, forthe purpose specified.

2. The combination of a series of flat parallel annular flanges, B O DE, constructed according to the formula of relative proportions hereinspecified, to form a'ventilating-cap.

3. In combination with the annular plates B G D E, the strips F,fashioned as set forth, and secured as described.

LEWIS F. BETTS. Witnesses:

HENRY G. WHITNEY, JEWIS F. JACOBS.

